diff --git a/keystore2/src/crypto/crypto.cpp b/keystore2/src/crypto/crypto.cpp
index e4a1ac3..5d360a1 100644
--- a/keystore2/src/crypto/crypto.cpp
+++ b/keystore2/src/crypto/crypto.cpp
@@ -225,7 +225,7 @@
 
 EC_KEY* ECKEYGenerateKey() {
     EC_KEY* key = EC_KEY_new();
-    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp521r1);
     EC_KEY_set_group(key, group);
     auto result = EC_KEY_generate_key(key);
     if (result == 0) {
@@ -251,7 +251,7 @@
 EC_KEY* ECKEYParsePrivateKey(const uint8_t* buf, size_t len) {
     CBS cbs;
     CBS_init(&cbs, buf, len);
-    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp521r1);
     auto result = EC_KEY_parse_private_key(&cbs, group);
     EC_GROUP_free(group);
     if (result != nullptr && CBS_len(&cbs) != 0) {
@@ -262,7 +262,7 @@
 }
 
 size_t ECPOINTPoint2Oct(const EC_POINT* point, uint8_t* buf, size_t len) {
-    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp521r1);
     point_conversion_form_t form = POINT_CONVERSION_UNCOMPRESSED;
     auto result = EC_POINT_point2oct(group, point, form, buf, len, nullptr);
     EC_GROUP_free(group);
@@ -270,7 +270,7 @@
 }
 
 EC_POINT* ECPOINTOct2Point(const uint8_t* buf, size_t len) {
-    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp521r1);
     EC_POINT* point = EC_POINT_new(group);
     auto result = EC_POINT_oct2point(group, point, buf, len, nullptr);
     EC_GROUP_free(group);
diff --git a/keystore2/src/crypto/lib.rs b/keystore2/src/crypto/lib.rs
index db23d1f..5f8a2ef 100644
--- a/keystore2/src/crypto/lib.rs
+++ b/keystore2/src/crypto/lib.rs
@@ -346,7 +346,7 @@
 
 /// Calls the boringssl EC_KEY_marshal_private_key function.
 pub fn ec_key_marshal_private_key(key: &ECKey) -> Result<ZVec, Error> {
-    let len = 39; // Empirically observed length of private key
+    let len = 73; // Empirically observed length of private key
     let mut buf = ZVec::new(len)?;
     // Safety: the key is valid.
     // This will not write past the specified length of the buffer; if the
@@ -381,8 +381,8 @@
 
 /// Calls the boringssl EC_POINT_point2oct.
 pub fn ec_point_point_to_oct(point: &EC_POINT) -> Result<Vec<u8>, Error> {
-    // We fix the length to 65 (1 + 2 * field_elem_size), as we get an error if it's too small.
-    let len = 65;
+    // We fix the length to 133 (1 + 2 * field_elem_size), as we get an error if it's too small.
+    let len = 133;
     let mut buf = vec![0; len];
     // Safety: EC_POINT_point2oct writes at most len bytes. The point is valid.
     let result = unsafe { ECPOINTPoint2Oct(point, buf.as_mut_ptr(), len) };